5 Nov
1999
5 Nov
'99
9:19 a.m.
In article <m11joav-000IyNC@p850ug1>, ard(a)p850ug1.demon.co.uk (Tony Duell)
wrote:
Only slightly. I have a software background and while I can (in principle)
understand a processor down to the gate level, I have only a very vague
idea of how things work electrically. I hope to remedy that this winter.
Well, considering the 1A fuse didn't blow instantly, I would suspect a
short in the load on the secondary side of the transformer. Time to
disconnect the secondaries and see if a 0.25A fuse holds. If it does,
reconnect the secondareis one at a time until the fuse blows and then
start tracing what's shorted. It may be as simple as a shorted rectifier
or smoothing capacitor (we can always hope :-))
The secondary end doesn't appear to be shorted, and the fuse blows
anyway :-( Unless I've made a mistake, things look pretty simple
(where + is a connection and -|- is not):
L----Fi----+---+--switch------1(| t |)5--+----fuse2---A front
120V lt | +--fuse1----+--2(| r |)6--|--+---------B panel
N----er--+-|---------------|--3(| n |)7--+ |
| | +--4(| s |)8-----+
other
fuse1 = 1/4 A 250V
fuse2 = 3/4 A 250V
switch = (part of) the main power switch.
trns = "DALE IPL-2329-25 105P80342 8445"; properties not marked.
Fuse1 is the one that blows instantly. AB leads to the front panel only.
With the power switch off, and the front panel disconnected (i.e. no
load except the meter), a 1A fuse at fuse1 lasts about two seconds,
during which time I measure about 15V across AB.
--
Kevin Schoedel
schoedel(a)kw.igs.net
[...]
The older PERQs were totally user-microprogrammable. You got the
assembler and the 'placer' with the OS distribution IIRC. And there was
some documentation in the manual. Mind you, the PERQ OS manual always
struck me as being a quick-reference guide for people who knew the system
-- a lot of information is either missing or hidden.
In my (commerical) experience more often missing than hidden. Vital
details noted only in the margin of a single copy of the manual, scribbled
after a telephone conversation with the designer, because no one ever
thought to, or had time to, document them fully. Of course some things
are hidden *as well*, but at least things which are merely hidden might
eventually be released.
The PERQ 3a (aka AGW3300) had a 68020 in it (:-(, not
microprogrammable).
But there was a graphics processor built from 2 29116 'ALUs', one for the
data path and one to calaculate addresses. That was user
microprogrammable, although AFAIK, tools for programming it were never
available.
I'm in an almost uniquely fortunate position of being able to generate
usable microprogramming tools with very little effort.
I suspect you
could work out more in 10 minutes than I could in 10 days.
In 10 minutes I could *probably* find the power switch -- if it's not
behind a door.
You exagerate, I think :-) Seriously, I'm fed up with 'technical'
manuals that contain no
schematics, no pinouts, no register bit allocations, etc. That's _not_ a
technical manual!
Sometimes it's even worse. Try explaining to a client that no, we
really *can't* write an assembler if they want to keep the instruction
encodings secret.
The previously-mentioned manual for this machine appears to be an
architecture manual rather than a hardware manual as such (although,
since it's in the form of a set of scans, I haven't had time to read
much beyond the table of contents yet), so it isn't any help for this
problem. Both it and the Daybreak manual do appear to document the
microinstructions, though.
I suppose you could also trace what the fuse is
connected to...
One side is straight on the line; the other is connected to a small
transformer on the fuse board. The secondaries lead to the front panel....